So your dentist says one of your front teeth needs to have a crown replaced. He or she shows you the defect on the x-ray or a clinical photo, and you book your appointment to have the procedure done.
...Have you ever wondered what actually goes on during the process? How do they get the old crown off... how do they make sure the new crown fits perfectly.. why do they have to drill so gosh darn much if there was a crown on there before?!
In this video, I use a surgical operating microscope to film the removal of a defective crown and replacement with a new custom crown.
For those of you who would prefer to read the steps as you watch, here you go:
1) local anesthesia / dental freezing (not shown in video) - we use a topical anesthetic (a numbing jelly) that makes the gums quite numb so that the patient either doesn't feel the injection or barely feels it. The jelly works great on the cheekside of the top arch (where we inject for most upper fillings), moderately well on the lower arch (where we inject for most lower fillings), and has a more mild effect for the palate side of the upper teeth (only need to freeze this area for difficult crowns, extractions and root canals).
2) split the old crown into two - we use the dental drill to carefully divide the old crown into two pieces; as the romans did to the celts... DIVIDE AND CONQUER. If we just tried to yank off the old crown, you risk breaking part of the tooth, or sometimes even pulling the tooth out!
3) clean up the decay / cavity - we don't want to leave infected tooth bits under the new crown. We remove all of the tooth decay and make sure we have only healthy tooth structure left behind.
4) fill the tooth - WAIT. Why do we need to fill the tooth if we're gonna put a crown on it?! Well, removing the cavity often leaves a very irregular shape in the tooth. If we expect the crown to slide on the tooth easily and intimately for a good fit, we need a smooth and regular shape to our tooth nub.
5) trim (prepare) the tooth - we then spend a LOT of time trimming the tooth down to size, polishing margins (i.e. the junction between the tooth and would-be crown), and engineering a tooth design that will allow for sufficient strength both of the tooth nub, and the crown that will sit on it.
6) get the gums out of the way - once the tooth is ready to be digitally imaged or have its shape recorded with impression material (kind of like taking a thumbprint of your tooth... a toothprint!), we need to make sure the gums are out of the way so the lab technician making the crown can tell EXACTLY where the crown should end, and where the natural tooth starts. We accomplish this by packing a few tiny braided cords in between the tooth and the gums. This pushes the gums out of the way, and also stops any bleeding so we can get a really really clean image or impression.
7) acquire the digital/analog impression: pretty.. self.. explanatory... to clarify though, we use a special camera for the digital impression, and dental goop (not the technical term) for analog impressions... (i.e. toothprints)
8) wait for lab to make the crown: DIGITAL - same day. ANALOG - one to two weeks.
9) prepare the tooth for cementation: We use a particle abrasion device to clean off any imaging powder or debris from the tooth nub. We also pack another cord (which will be removed later) to make sure no fluid creeps up from the gums underneath the crown.
10) Cement the crown! We fill up the crown with the cement, plop it on the tooth nub ("plop" doesn't impart a sense of precision, but we really do have to be careful in the delivery of these crowns as they are super slippery sometimes), and shine our special cement-setting light on the tooth. After 1 second, the excess cement that squeezed out between the crown and tooth nub is already hard and ready to be peeled away. Once everything is cleaned up, we check the bite, and dismiss our patient.
There you have it folks! Thanks for reading and tuning in for this week's tooth minute tuesday. Leave me a comment on one of my youtube videos if you'd like certain topics addressed in future blogposts/videos.
See you next week,